ERBB2 and breast carcinoma: Recent advancements in single-cell transcriptomics have elucidated the degree of molecular subtype plasticity in MBC, revealing how tumor cells can transition among established breast cancer subtypes, including Luminal A/B, HER2-enriched (Ferrer et al., 2025), and triple-negative (TNBC) states (Jie et al., 2025).